In some machinery relating to paper manufacturing, paper webs of the machine reels can be joined so that the post processing can be applied in a continuous manner. For example, in coating machines that are not part of the paper machine, the machine reels can be unwound through the coating machine one-by-one such that the paper can be spliced at full speed. The splicing of paper web refers to a process in which once a machine reel has become empty, the paper from a new machine reel can be attached to the paper from the previous reel so that the post-processing machine can run in continuous manner.
In splicing, the paper from the new machine reel can be glued or taped to the paper of the previous reel before the material in the previous reel ends. The remaining material length is estimated via rate of change in roll diameter, paper thickness calculation and speed. The new reel of material can be prepared by placing glue or two-sided tape to the surface of the material along the width of the reel. The new reel is accelerated such that the surface speed of the new reel corresponds with the speed of the web from the previous reel. The new reel-roll acceleration is initiated well in advance to be fully ready and stable before the splice takes place and material from previous reel runs out. The foreseen time of splice may have some inaccuracy, which is why sufficient time margin is added at a starting point.
When the new reel has reached the desired speed and position, a separate splicing roll or brush pushes the web from the previous reel to the surface of the new reel. The applied glue or tape attaches the webs together after which the web from the previous reel is cut. This way the post-processing machinery, such as an off-machine coating machine, can run continuously without interruptions.
In a splicing process the amount of material left in the emptied reel can be minimized so that as little as possible material is wasted. The tail of the material in the emptied reel can be problematic because after the web has been cut, the material from the previous reel can keep on unwinding for a few more seconds before stopping. This hanging tail can lead to unwanted breaks in the web when it, or parts of it, ends in the route of the new web. Mechanical brakes can be used for braking the emptied reel to stop it as fast as possible for avoiding the problems relating to the hanging tail.
WO 00/40491 discloses a method in which the amount of material left in the emptied reel can be minimized. The minimization can be carried out by gluing the paper layers together near the bottom of the reel, thus preventing the paper to unwind past this point. Making use of this requires the splicing and cutting to happen very close but still before the glued bottom layers appear, so that the cut and hanging tail can be stopped by the glue before any excess unwinding. The position of the bottom glue is identified to the system by a premark in the edge of the web, for example, a fixed distance before. The premark is done together with the bottom glue, in roll preparation area, before the coater.
In known splicing methods, such as in U.S. Pat. No. 4,077,580, when the diameter of the old reel reaches a certain value, the new reel is accelerated to the required splicing speed. The acceleration is carried out with constant parameters. The start of the acceleration takes place in good time before the actual splicing so that the new reel may rotate for minutes.
When the conditions for splicing are met, i.e., the diameter of the old reel reaches another limit, the angular position of the new reel is unknown or at least not predicted. This means that the splicing instant must be delayed until the new reel reaches a known position and then the required position for starting of the splicing. It may take up to one rotation of the new reel for waiting of the known and the required position, and the splicing can be started only after one more rotation of the new reel. Thus, when the conditions for splicing are met, the new reel is still be rotated one to two rotations, which can equal approximately 10 to 22 meters of paper from the old reel.
One of the disadvantages associated with the above methods is that the methods still leave unnecessary tail on the emptied reel. The tail can be up to the length corresponding the whole circumference of the new reel plus distance from emptied reel paper tangent to the cutting device plus the safety margin.
Further, the new reel is rotated somewhat longer than required, which may affect the adherence of the splice because the glue or tape on the surface of the rotating roll dries quickly.